This really is a rather small nerf. The only true purpose of this talent is to stay on target during Shadowdance, you'll still be able to do that to every class other than Warriors who Heroic Leap away, although if you time it right you can still jump to them in mid air, so you'll still be able to stay on them too.

It's still lightyears ahead of Shadowstep in every offensive situation right now, the only way this talent won't be worth taking is if they change the metagame to be less bursty, or if they buff Shadowstep somehow.

This is actually a significant nerf. C&D was arguably OP, but its effectiveness will be far weaker vs several classes. e.g getting gripped off the target, displacer beast, on accounts of the added movement speed, blink+blazing speed, disengage, Intervene, teleports and Leap of Faith will be more effective, probably some others. Sure, you might be able to catch your target after a little running, but remember the damage window for this ability.

wont be a huge effect for my rogue alt, 10 yards isnt a huge difference with the assorted other tools we got
im just glad they havnt touched our other abilities for the moment

May not sound like much but 10 yards is a LOT. Even going from shadowstep 25 yards to C&D 30 yard is fairly noticable when you are used to the 30 yard range.

Will be much harder to land focus garrotes and cheap shots etc now and as poster above you said, escapes coupled with speed boosts and lag will definitely be felt big time when target gets out of range quickly.

That will change nothing. Rogues will just move to one of the other burstier talents and people will cry to nerf burst.

If you ask the community this is what would happen:

Sutrefuge reworked to only give 1 second of stealth.
Ambush and Evsicerate straight 30% damage nerf.
Cloak of shadows on 3 minute cooldown.
Removal of preparation.
Shadow dance moved to a 3 minute cooldown.

Pretty much anyone not a rogue will think this is a good list of future nerfs combined with the nerfs that are now on ptr. Only it will of course totally remove rogues from PvP.